Navegando por Autor "Santos, Antonio Carlos dos"

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ArticleNeuroimaging in stroke and non-stroke pusher patients
(2011-07-11) Santos-Pontelli, Taiza Elaine Grespan; Pontes-Neto, Octavio Marques; Araújo, Dráulio Barros de; Santos, Antonio Carlos dos; Leite, João Pereira
Pusher behavior (PB) is a disorder of postural control affecting patients with encephalic lesions. This study has aimed to identify the brain substrates that are critical for the occurrence of PB, to analyze the influence of the midline shift (MS) and hemorrhagic stroke volume (HSV) on the severity and prognosis of the PB. We identified 31 pusher patients of a neurological unit, mean age 67.4±11.89, 61.3% male. Additional neurological and functional examinations were assessed. Neuroimaging workup included measurement of the MS, the HSV in patients with hemorrhagic stroke, the analysis of the vascular territory, etiology and side of the lesion. Lesions in the parietal region (p=0.041) and thalamus (p=0.001) were significantly more frequent in PB patients. Neither the MS nor the HSV were correlated with the PB severity or recovery time. Key words: pusher behavior, stroke, postural control.
Behavioral and neuroimaging responses induced by mental imagery of threatening scenarios
(2016-10-15) Shuhama, Rosana; Rondinoni, Carlo; Araújo, Dráulio Barros de; Caetano, Gustavo de Freitas; Santos, Antonio Carlos dos; Graeff, Frederico Guilherme; Del-Ben, Cristina Marta
Functional neuroimaging studies have shown that actual situations of uncertain or distant threats increase the activity of forebrain regions, whereas proximal threats increase the activity of the dorsal midbrain. This experiment aimed at testing the hypothesis that brain activity elicited by imagined scenarios of threats with two different magnitudes, potential and imminent, resembles that found in response to actual threats. First, we measured subjective responses to imagined scenarios of potential and imminent threats compared with neutral and pleasant scenarios. The same scenarios were used as a paradigm in a functional magnetic resonance imaging experiment. Behavioral results show that the scenarios draw a gradient of hedonic valence and arousal dimensions. Both potential and imminent threat scenarios increased subjective anxiety; the imminent threat scenario also increased feelings of discomfort and bodily symptoms. The functional magnetic resonance imaging results revealed modulations of BOLD signal in the ventromedial prefrontal cortex by potential threat and in the periaqueductal gray matter by imminent threat. These results agree with previously reported evidence using actual threat situations, indicating that mental imagery is a reliable method for studying the functional neuroanatomy of relevant behavioral processes.
Neurofunctional changes after a single mirror therapy intervention in chronic ischemic stroke
(2018-03-20) Novaes, Morgana M.; Palhano-Fontes, Fernanda; Peres, Andre; Mazzetto-Betti, Kelley; Pelicioni, Maristela; Andrade, Kátia C.; Santos, Antonio Carlos dos; Pontes-Neto, Octavio; Araújo, Dráulio Barros de
Background: Mirror therapy (MT) is becoming an alternative rehabilitation strategy for various conditions, including stroke. Although recent studies suggest the positive benefit of MT in chronic stroke motor recovery, little is known about its neural mechanisms. Purpose: To identify functional brain changes induced by a single MT intervention in ischemic stroke survivors, assessed by both transcranial magnetic stimulation (TMS) and functional magnetic resonance imaging (fMRI). Materials and methods: TMS and fMRI were used to investigate 15 stroke survivors immediately before and after a single 30-min MT session. Results: We found statistically significant increase in post-MT motor evoked potential (MEP) amplitude (increased excitability) from the affected primary motor cortex (M1), when compared to pre-MT MEP. Post-MT fMRI maps were associated with a more organized and constrained pattern, with a more focal M1 activity within the affected hemisphere after MT, limited to the cortical area of hand representation. Furthermore, we find a change in the balance of M1 activity toward the affected hemisphere. In addition, significant correlation was found between decreased fMRI β-values and increased MEP amplitude post-MT, in the affected hemisphere. Conclusion: Our study suggests that a single MT intervention in stroke survivors is related to increased MEP of the affected limb, and a more constrained activity of the affected M1, as if activity had become more constrained and limited to the affected hemisphere.
Persistent pusher behavior after a stroke
(2011) Santos-Pontelli, Taiza Elaine Grespan; Pontes-Neto, Octavio Marques; Araújo, Dráulio Barros de; Santos, Antonio Carlos dos; Leite, João Pereira
Pusher behavior (PB) is a postural control disorder characterized by actively pushing away from the nonparetic side and resisting passive correction with a tendency to fall toward the paralyzed side.1 These patients have no awareness that their active pushing is counterproductive, which precludes the patients from standing without assistance. Several studies have already demonstrated that PB can occur in patients with lesions in both hemispheres, and PB is distinct from neglect and anosognosia.2-8 The high frequency of the association between PB and neurophysiological deficits might reflect an increased vulnerability of certain regions to stroke-induced injury rather than any direct involvement with the occurrence of PB.9,10 Traditionally, PB has only been reported in stroke patients; however, it has also been described under nonstroke conditions.8 Previous imaging studies have suggested the posterolateral thalamus as the brain structure that is typically damaged in pusher patients.4,11 Nevertheless, other cortical and subcortical areas, such as the insular cortex and post-central gyrus, have also been highlighted as structures that are potentially involved in the pathophysiology of PB.2,12-16

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Navegando por Autor "Santos, Antonio Carlos dos"